1. Field of the Invention
This invention relates to a semiconductor laser array device which is composed of a single semiconductor laser device having a plurality of resonators (i.e., active waveguides) for laser oscillation optically coupled therebetween, resulting in a semiconductor laser device with which high optical output power operation can be achieved.
2. Description of the prior art
Phase-synchronized laser arrays have been proposed in which a plurality of active waveguides are disposed in a parallel manner in a single semiconductor laser device to attain optical phase coupling therebetween, resulting in a laser device producing great output power with a single phase. One of these laser arrays in a CSP-LOC (channeled-substrate planar large-optical-cavity) laser device using a channeled substrate proposed by D. Botez et al., of RCA Laboratories, Fourth International Conference on Integrated Optics and Optical Fiber Communication, Abstract 29B52, June 27-30, 1983, Tokyo, Japan, which is shown in FIG. 2. This laser device is produced as follows: On an n.sup.+ -GaAs substrate 11 having a plurality of striped V-channels in a parallel manner thereon, an n-GaAlAs cladding layer 12, an n-GaAlAs optical guide layer 13, a GaAlAs active layer 14, a p-GaAlAs cladding layer 15, and a p.sup.+ -GaAs cap layer 16 are successively grown, followed by subjection to a vapor deposition treatment to form a SiO.sub.2 insulating layer as an electric current blocking layer on the cap layer 16. Then, an ohmic electrode 18 is formed on the cap layer 16 and the insulating layer 17, resulting in the CSP-LOC laser device. This laser device has a disadvantage in that the amount of laser light absorbed into the GaAs substrate varies depending upon the distance from the active layer to the mesa-portion of the substrate. If the distance between the active layer and the mesaportion of the GaAs substrate is small, the amount of laser light absorbed into the GaAs substrate becomes great so that the laser device cannot produce high output power. If the distance therebetween is great, the refractive index difference required for stable laser oscillation cannot be created. Thus, a zero shift in the optical phase between the adjacent laser operation areas is unattainable.